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Body Logistics Revision > 4 - Epithelial Cells & Specialisations > Flashcards

4 - Epithelial Cells & Specialisations Flashcards

1
Q

What does a mucus membrane line?

A

Internal tubes that open to the exterior (e.g. GI, respiratory and urinary tracts)

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2
Q

What are serous membranes?

A

Thin, two-part membranes which line closed cavities and envelope the viscera. E.g. peritoneum, pleura, pericardium

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3
Q

What do serous membranes secrete and what does this do?

A

Watery lubricating fluid

Promotes friction-free movement of the structures they surround.

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4
Q

What layers does a serous membrane consist of?

A

Simple squamous epithelium - secretes lubricating fluid

Thin layer of connective tissue - attaches epithelium to adjacent tissues

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5
Q

How do serous membranes develop around organs?

A
  • During embryogenesis, the heart, lungs and gut invaginate into a bag-like cavity
  • They become surrounded by a membrane with an inner (visceral) and outer (parietal) layer, with fluid inside
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6
Q

The epithelial lining of blood vessels and lymphatic is called …..

A

Endothelium

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7
Q

What are the different types of simple epithelial cell?

A
  • Squamous
  • Cuboidal
  • Columnar
  • Pseudostratified
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8
Q

What are the different types of stratified epithelia?

A
  • Squamous
  • Cuboidal
  • Columnar
  • Transitional
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9
Q

What are the functions of simple squamous epithelia?

Give some examples of it’s location.

A
  • Fast material exchange
  • Barrier to fluids
  • Tissue lubrication

E.g. vasculature, bowman’s capsule, serosa of lungs, heart and viscera

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10
Q

What are the functions of simple cuboidal epithelium?

Give some examples of their location.

A
  • Absorption and conduit
  • Absorption and secretion
  • Barrier/covering
  • Hormone synthesis and storage

E.g. pancreatic duct, kidney collecting duct, thyroid gland follicles

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11
Q

What role does simple cuboidal epithelium play in the thyroid gland?

A
  • Lines the thyroid follicles
  • Synthesises thyroglobulin and stores it outside the cell in the centre of the follicle (colloid) - only organ that does this!
  • Reprocesses thyroglobulin to thyroxine, which is released into capillaries
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12
Q

In simple columnar epithelium, where is the nucleus positioned?

A

Close to the basal lamina

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13
Q

What are the functions of simple columnar epithelium?

Give examples of where this can be found.

A
  • Absorption
  • Secretion
  • Lubrication

E.g. Stomach and gastric glands, small intestine, colon and gallbladder

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14
Q

In the crypts of Lieberkühn, what are the white ‘holes’ in the epithelium seen on histology? What do they do?

A

Goblet cells

Secrete mucus (mucins and water)

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15
Q

What structure can sometimes be found on simple columnar epithelium to increase surface area?

By what method can this be seen?

A

Microvilli

Only visible under electron microscope

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16
Q

The villi of the small intestine contain ………. veins, a type of lymphatic vessel to draw liquid from the gut

A

Lacteal

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17
Q

What is pseudostratified epithelium?

A
  • All cells make contact with the basement membrane
  • Not all reach the apical surface
  • Nuclei lie at different levels, giving the appearance of multiple layers
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18
Q

What are the functions of pseudostratified epithelium?

Give examples of where this is found.

A
  • Secretion and conduit
  • Mucus secretion
  • Particle trapping and removal

E.g. Nasal cavity, trachea, bronchi, ductus deferens

19
Q

What is stratified squamous epithelium and what does it do?

A
  • Multiple layers of cells, the outermost layer is thin squamous cells
  • Can be non-keratinised or keratinised

Functions:

  • Protection from abrasion
  • Reduces water loss but remains moist
20
Q

Give some examples of where stratified squamous (non-keratinised) epithelium is found and why.

A

The vagina - prevents abrasion and reduces water loss. Cells are also rich in glycogen, metabolised by lactobacilli which make lactic acid (low pH for destroying pathogens)

The oesophagus - prevents abrasion and keeps lining moist

Also found in oral cavity, anal canal, surface of corneas and inner side of eyelids

21
Q

What is keratinised stratified squamous epithelium?

What is the outermost layer called?

A
  • Stratified squamous epithelium where the outermost cells have lost their nuclei and become cornified (filled with keratin)
  • The outermost layer is the stratum corneum
22
Q

What are the functions of stratified squamous keratinised epithelium?

A
  • Protect against abrasion and trauma
  • Prevent water loss
  • Prevent microbial ingress
  • Shielding from UV damage
23
Q

What is the primary site of stratified squamous keratinised epithelium?

A

The epidermis of the skin

24
Q

What is the structure of the skin dermis?

A
  • Dense, irregular, connective tissue

- Contains collagen and elastin in all directions

25
Q

Which layer of the skin is thicker in thick skin (e.g. soles of feet)?

A
  • More keratinised epidermis - as it is more likely to be abraded
  • Living epidermal cells and the dermis are the same
26
Q

Epithelial cells in stratified squamous keratinised epithelium are called …….

A

Keratinocytes

27
Q

Describe the process of keratinocyte division and migration.

A
  • Keratinocyte mitosis occurs in the basal layer of the epidermis
  • Daughter cells move towards the surface, differentiate and lose ability to divide
  • Cells synthesise keratins which contribute strength to the epidermis
  • Normal transit time from basal -> stratum corneum is 28-40 days
28
Q

The transit time for keratinocytes to reach the stratum corneum is reduced in certain diseases.

Give an example of one of these diseases and the change seen in transit time.

A

Psoriasis

Transit time reduced to 2-4 days (normally 28-40)

Stratum corneum is produced in abundance as silvery scales

29
Q

What are melanocytes and what do they do?

A
  • In the basal layer of epidermis
  • Produce melanin - pigment of skin colour
  • Sends dendritic processes into the upper layers of the skin and can transfer pigment into the keratinocytes
  • Can produce more/less melanin but everyone has the same number of melanocytes
30
Q

What are langerhans cells (in epidermis) and what do they do?

A
  • Highly specialised antigen-presenting cells (present to T-lymphocytes)
  • Mediate immune reactions (e.g. allergic contact dermatitis)
31
Q

What is transitional epithelium and where is it found?

A
  • Cells vary in shape (columnar, cuboidal or squamous)
  • In tissues with distensibility (relaxed -> stretched)

Urinary epithelium (urothelium)

32
Q

What are the functions of transitional epithelium?

A
  • Distensibility

- Protection of underlying tissue from toxic chemicals

33
Q

What are goblet cells?

A
  • Specialised cells in epithelia that release mucins via exocytosis
  • Water released by release of ions
  • Have microvilli to increase surface area
34
Q

What causes cystic fibrosis?

How are tissues of the body affected?

A
  • Mutation in the CFTR gene (a chloride channel responsible for the movement of water that thins the mucus)
  • Clogging and infection of the airways, breathing obstruction
  • Blocked bile duct, pancreatic duct and reproductive tracts
  • Thick, non-motile stools in small intestine
  • Salty sweat and crystals on the skin
35
Q

What are club (clara) cells?

A
  • Found on the airway side of terminal bronchioles
  • Protect the epithelium with secretory proteins and secrete solutions similar to pulmonary surfactant (breaks surface tension for gas exchange)
  • Detoxify substances (CytP450 enzymes in SER)
  • Also act as stem cells to regenerate respiratory epithelium
36
Q

What are microfold cells?

A
  • Found in the small intestine close to lymphatic nodules
  • Trap pathogens and present to underlying dendritic cells, lymphocytes and macrophages
  • Also a weak point for the epithelium, pathogens can exploit as a point of entry
37
Q

What happens in the early stages of smoking damage to the lungs?

A
  1. Normal mucus layer thickens

2. Cilia die off (regeneration of cilia takes 2-4 days)

38
Q

What happens in the chronic stages of smoking damage to the lungs?

A
  1. Goblet cells and basal cells proliferate
  2. Club cells die
  3. Carcinogens induce mutations and malignancy
  4. Pneumocytes in alveoli die
39
Q

What is acute bronchitis?

A
  • Cough and mucus production
  • Breathlessness (< 3 months)
  • Due to inflammation, swelling and narrowing of airways and excess mucus
  • Increased risk of respiratory diseases
40
Q

What is chronic bronchitis?

A
  • Cough and mucus production
  • Chronic inflammation (> 3 months)
  • Inflammation, swelling and narrowing of airways
  • Excess mucus
  • Irreparable damage to bronchioles and alveoli
41
Q

What is emphysema?

A
  • Shortness of breath due to permanent widening of the alveoli without fibrosis
  • Damage to the air sacs, loss of elastic recoil and permanent change to size of alveoli
42
Q

What is COPD?

A

Chronic Obstructive Pulmonary Disease (COPD)

Emphysema and chronic bronchitis

43
Q

What is asthma?

A
  • wheeze, shortness of breath, chest tightness, cough
  • variable expiratory airflow limitation
  • caused by bronchospasm (tightens smooth muscle layer)
  • obstruction caused by mucus and narrowing of conducting airways
  • often has a trigger (e.g. cold, exercise, allergens, stress)

Body Logistics Revision (25 decks)

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